The present invention relates to an assembly of several layers having one or more reinforcing layers and to fiber reinforced plastic articles which have a resinous matrix and a reinforcing material.
Fiber reinforced plastic articles which have a resinous matrix and a reinforcing material are known.
In general, such composite parts are made from at least one, typically multiple reinforcing layers which are impregnated with a resin. The layers may be laid in place one layer at a time and then be impregnated with a resin. Alternatively, a prefabricated multiple layered structure, such as disclosed in U.S. Pat. No. 4,410,577 may be impregnated with a resin. The layered assembly is then cured, generally under heat and pressure, by conventional processes dependent on the resin system in use.
These fiber reinforced plastic articles have numerous known applications, particularly as structural components in airplanes, ships, boats and automobiles. One of their major advantages is their high strength at a low weight.
Frequently, the reinforcing layers in the plastic articles are in the form of a woven fabric. After curing the resin which forms the matrix of the plastic article, it is often desired to apply a finishing layer such as a paint or lacquer layer to the plastic article, especially when the article is intended to be used as an airplane, ship or car body part.
However, due to the weave pattern of the reinforcing layers, it is often difficult, or even impossible, to obtain a smooth surface of the plastic article after curing. Accordingly, even after applying a finishing layer, the weave pattern is still visible, which is generally undesirable. Another disadvantage of the reinforced plastic articles which do not have a smooth surface is the difficulty of avoiding voids or air bubbles when the finishing layer is applied.
U.S. Pat. No. 4,574,106 relates to a composite sheet consisting of a sheet of aluminium bonded to a mat of fiberglass which is bonded to several layers of fiberglass cloth. The mat of fiberglass should serve as a smooth finish when aluminium is removed after resin has been injected into the fiberglass cloth. Unfortunately, U.S. Pat. No. 4,574,106 neither addresses to nor solves the above described problems of surface imperfections in a mat of fiberglass.
U.S. Pat. No. 4,044,188 addresses to the problem of surface imperfections caused by the reinforcing materials embedded in the thermoplastic resin. It is suggested to produce a composite sheet which consist of a glass mat formed of long glass fibers which mat adheres, with a thermoplastic resin as a binder, to a surface layer consisting of (a) a thermoplastic resin, (b) short glass reinforcing fibers which are aligned parallel to the plane of the sheet and (c) a particulate filler. The short glass fibers and the filler are said to avoid migration of the glass mat reinforcement to the surface of the sheet during sheet fabrication. Unfortunately, the separate production of the surface layer for the specific use in the composite sheet is costly. Furthermore, the variety of materials which can be used for the composite sheet and the range of the weight ratios between these materials are limited which limits the use of composite sheet.
French Pat. No. 2 083 561 (equivalent to British Pat. No. 1341438) relates to a composite sheet containing (a) 30 to 95 weight percent of a thermoplastic resin, (b) 5 to 70 weight percent of thick glass fibers, (c) 0 to 60 weight percent of a filler and (d) 17 to 340 g/m thin fibers in the form of a non-woven mat at the surface of the composite sheet. The sum of (a), (b), (c) and (d) is 100 weight percent. The thin fibers are for example produced of glass, polyester or polyamide. The surface of the composite sheet is more rich in resin than the rest of the composite sheet. French Pat. No. 2 083 561 teaches that the composite sheets have a smooth surface because of the particular combination of thin and thick fibers. Unfortunately, due to the particular combination of thin and thick fibers, the usefulness of the composite sheets is limited.
Accordingly, an object of the present invention is to provide other fiber reinforced plastic articles which have a smooth surface, i.e., a surface without substantial surface imperfections.
Furthermore, another object of the present invention is to provide other fiber reinforced plastic articles which can be coated with a finishing layer, such as a paint or lacquer, which have substantially no air bubbles or voids therein.
Yet another object of the present invention is to provide an assembly of several layers having one or more reinforcing layers which is useful as a reinforcing material for producing said fiber reinforced articles.